This proposed research uses 1996 through 2000 Medicare and Medicaid eligibility and claim files for Michigan residents linked with the Michigan Cancer and Death Certificate Registries to create an inception cohort of newly diagnosed cancer patients. This cohort will be identified by Medicaid eligibility status (dually eligible versus Medicare only). We propose to examine disparities in the incidence of breast, colorectal, lung, and prostate cancer, the stage of these diseases at diagnosis, treatment afforded to patients and associated costs of care, and the survival time following diagnosis. This research seeks to expand knowledge regarding the complex interactions among the social, personal, racial, and health system variables that create and influence disparities along the cancer trajectory. We test a systematically derived set of hypotheses and seek to determine how disparities identified early in the trajectory influence disparities at later points in the trajectory. For example, does later stage at diagnosis lead to less appropriate care that leads to higher costs and shorter survival? An examination of the impact of disparities in cancer detection and/or treatment on survival is one of the significant additions of this research to the state of the science. We have four simply stated aims that are analytically highly complex. Our aims are targeted at two populations of interest--persons dually eligible for Medicare and full Medicaid benefits and persons eligible for Medicare without Medicaid (for the purposes of this application, referred to as "Medicare only.") These aims are: 1) Measure the cancer incidence rates in dually eligible and Medicare only beneficiaries; 2) Compare stage of diagnosis for dually eligible and Medicare only beneficiaries; 3) Compare treatment delivery between the two groups and estimate the cost of care; and 4) Measure survival rates for dually eligible and Medicare only beneficiaries.